The men were not true followers of the Islamic faith, according to the influential Muslim Jama Masjid Trust, which runs the 7.5-acre Badakabrastan graveyard in central Mumbai.
"People who committed this heinous crime cannot be called Muslim," said Hanif Nalkhande, a trustee. "Islam does not permit this sort of barbaric crime."
Ten gunmen laid siege to India's financial capital. One was captured and the rest killed.
The bodies of the nine now lie in a morgue awaiting last rites, while the lone surviving militant is in police custody.
Normally, unclaimed bodies thought to be Muslims are given to the nearest Muslim graveyard for burial after three days, leaving police unsure what to do now.
Police do not believe anyone will claim the gunmen's corpses since they are thought to be from Pakistan.
"The gunmen must be buried because we are bound to see that their last rites are performed according to the religion they follow," said Jain Sirmukadam, a senior police inspector. "We have heard the trust's decision. We are considering what to do now."
There are seven other Muslim graveyards in Mumbai, but the Jama Masjid's influence means none of the others are likely to accept the bodies.
While Nalkhande said several Islamic scholars had backed the trust's decision, some also criticised the move.
Even militants must be given a proper burial, said scholar Maulauna Zubair Ahmed.
"As per the Shariah, the trust cannot say no," he said, referring to Islamic law. "The Shariah says whether a Muslim is a drunkard, rapist, criminal, you must offer him a place for burial."
Indian authorities say the captured gunman said he was trained at a camp in Pakistan run by the militant group Lashkar-e-Taiba. Authorities in Pakistan have denied this.